Preparation, characterization, and theoretical analysis of group 14 element(I) dimers: A case study of magnesium(I) compounds as reducing agents in inorganic synthesis

摘要

A synthetic route to the new amidine (DipNH)(DipN)- C(C_6H _4Bu~t-4) (ButisoH; Dip = C_6H_3Pr _2~i-2,6) has been developed. Its deprotonation with either LiBun or KN(SiMe_3)_2 yields the amidinate complexes [M(Butiso)] (M = Li or K). Their reactions with group 14 element halides/pseudohalides afford the heteroleptic group 14 complexes [(Butiso)SiCl3], [(Butiso)ECl] (E = Ge or Sn), and [{(Butiso)- Pb(μ-O _3SCF_3)(THF)}∞], all of which have been crystallographically characterized. In addition, the synthesis and spectroscopic characterization of the homoleptic complex [Pb(Butiso)2] is reported. Reductions of the heteroleptic complexes with a soluble magnesium(I) dimer, [{(~(Mes)Nacnac)Mg}2] (~(Mes)Nacnac = [(~(Mes)NCMe) _2CH]?; Mes = mesityl), have given moderate-to-high yields of the group 14 element(I) dimers [{(Butiso)E}_2] (E = Si, Ge, or Sn), the X-ray crystallographic studies of which reveal trans-bent structures. The corresponding lead(I) complex could not be prepared. Comprehensive spectroscopic and theoretical analyses of [{(Butiso)E}_2] have allowed their properties to be compared. All complexes possess E-E single bonds and can be considered as intramolecularly base-stabilized examples of ditetrelynes, REER. Taken as a whole, this study highlights the synthetic utility of soluble and easy to prepare magnesium(I) dimers as valuable alternatives to the harsh, and often insoluble, alkali-metal reducing agents that are currently widely employed in the synthesis of low-oxidation-state organometallic/inorganic complexes.